The singer's family always believed her death was accidental and was not a result of deliberate action taken by Houston—or anyone else, according to the insider.

While the actual cause of death was temporarily listed as "deferred" on Houston's death certificate pending the result of toxicology tests, "nothing suspicious" has been found to connect any physicians or other people of interest to Houston's case and the inquiry is nearing completion, the source says.

Plus, "she had no marks on her body whatsoever to indicate a struggle, and she was the furthest thing from trying to kill herself."

The L.A. County Department of Coroner will not comment, citing the ongoing investigation.

Our source says that the autopsy tox screen could be in the Beverly Hills Police Department's hands by next week and, depending on the status of other elements of their investigation, the case could be closed very soon afterward.

Sources have told E! News that Houston had prescriptions for antidepressants and anti-anxiety medications, and a handful of pill bottles were reportedly found in her room at the Beverly Hilton, where she was found dead in the bathtub.

One thing that isn't on the BHPD's plate is any investigation into who may have leaked photos of Houston's death scene to the media. Contrary to a RadarOnline report, Lt. Mark Rosen tells E! News that no members of Houston's family have reached out to them regarding any "death scene photos."